Neural Correlates of Spatial Navigation in Primate Hippocampus / 神经科学通报·英文版

The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.

Floor Maze Test as a predictor of cognitive decline in older adults living in nursing homes / Floor Maze Test como preditor de declínio cognitivo em idosos residentes de instituições de longa permanência

OBJETIVO: Pesquisas em instituições de longa permanência para idosos (ILPI) mostram uma associação entre o aumento de risco de declínio cognitivo e o comprometimento das habilidades de navegação espacial dos idosos. A navegação espacial pode ser definida como uma habilidade complexa, que depende de funções cognitivas e motoras, emergindo como um importante marcador de estadiamento da demência. O presente estudo teve por objetivo comparar a navegação espacial de idosos saudáveis; institucionalizados e com demência MÉTODOS: Foi realizado um estudo de corte transversal com 78 idosos (saudáveis = 37, demência = 22, institucionalizados = 19) avaliados por meio do Miniexame do estado mental (MEEM), Floor Maze Test (FMT) e 8-foot-up-and-go (8UG). Uma ANOVA One-way foi realizada para comparar os grupos. RESULTADOS: Como esperado, o grupo saudável foi mais ágil, tanto no FMT imediato (X2 = 31,23; p < 0,01) quanto no tardio (X2 = 41,21; p < 0,01). Quando comparados os grupos demência e institucionalizados, não houve diferença significativa no MEEM e FMT tardio. Porém, os idosos institucionalizados mostraram piores resultados que o grupo demência no FMT imediato (p < 0,01) e no teste 8UG (p < 0,01). CONCLUSÃO: Os resultados indicam um pior desempenho na navegação espacial, função executiva e habilidades motoras dos idosos em ILPI e com demência. A possibilidade de idosos institucionalizados serem subdiagnosticados deve ser considerada.

OBJECTIVE: Long-term care facilities (LTCF) are associated with an increased risk of cognitive decline and impairment in spatial navigation abilities. Recent studies have demonstrated that spatial navigation as a complex skill, involving cognitive and motor functions, emerging as a new marker for the progression of dementia. The present study aims to compare spatial navigation in healthy, institutionalized, and AD elderly subjects. METHODS: In a cross-sectional study, we evaluated 78 elderly individuals (healthy = 37, AD = 22, institutionalized = 19) using the Mini-Mental State Examination (MMSE), Floor Maze Test (FMT) and 8-foot-up-and-gotest (8UG) to assess global cognitive function, spatial navigation and motor function, respectively. RESULTS: In the FMT, the immediate maze time (IMT) and delay maze time (DMT) were significantly shorter in the healthy group than those of the institutionalized and AD groups (X2 = 31.23; p < 0.01) and (X2 = 41.21; p < 0.01), while there were no significant differences between the AD and institutionalized groups in terms of the DMT and MMSE results. However, the institutionalized group showed worse results in terms of IMT (p < 0.01) and 8UG (p < 0.01) than those in the dementia group. CONCLUSION: Our results indicate that both institutionalized older people and patients with Dementia have a deficit in the spatial navigation ability, cognitive functions and motor skills. We should consider that there might be a possibility of underdiagnosis in institutionalized older people.

Asociaciones entre función vestibular y habilidades cognitivas: un enfoque básico-clínico / Associations between vestibular function and cognitive abilities: from basic to clinical approach

RESUMEN El sistema vestibular tiene un rol fundamental en funciones sensorio-motoras, control del equilibrio y estabilidad de la mirada. En las últimas décadas un amplio número de trabajos ha descrito la importancia de las aferencias vestibulares en el funcionamiento de diversas áreas del cerebro relacionadas con funciones cognitivas tales como la atención, memoria, navegación y otras habilidades visuo-espaciales. Estudios en pacientes con vestibulopatía han demostrado que estos individuos presentan disminución de su rendimiento en algunas pruebas neuropsicológicas; y, a su vez, que personas con patología cognitiva como deterioro cognitivo leve y demencia por enfermedad de Alzheimer tienen mayor probabilidad de presentar pruebas vestibulares alteradas. Esta revisión se enfoca en el papel que cumple el sistema vestibular y su asociación con habilidades cognitivas; basándose en estudios básicos y clínicos que describen una red vestibular cerebral y que han llevado a proponer modelos teóricos que relacionan la función vestibular con la cognición.

ABSTRACT The vestibular system is widely known for its role in sensory-motor functions, balance control and gaze stability. In recent decades, several research articles have described the importance of vestibular afferents in the functioning of brain areas related to cognitive skills such as attention, spatial memory, spatial navigation and other visuospatial abilities. Studies involving subjects with vestibulopathy reveal that these individuals show decreased performance on neuropsychological tests; and that patients with neurocognitive pathologies, such as mild cognitive impairment and dementia due to Alzheimer's disease, have a greater probability of producing diminished or absent responses in clinical vestibular electrophysiological tests. This literature review focuses on the role played by the vestibular system and its association with cognitive abilities. The review incorporates a description of basic and clinical research that describe the cortical vestibular network and emerging theoretical models linking vestibular function to cognition.

Egocentric and allocentric spatial memory in healthy aging: performance on real-world tasks

Although normal aging has been related to several cognitive difficulties, other processes have been studied less, such as spatial memory. Our aim was to compare egocentric and allocentric memory in an elderly population using ecological tasks. Twenty-eight cognitively unimpaired participants performed Egocentric and Allocentric Spatial Memory Tasks, as well as Spatial Span from CANTAB, Benton's Judge of Line Orientation test (JoLO), and Montreal Cognitive Assessment test (MoCA). The results revealed that younger participants showed better performance than older participants on both the Egocentric and Allocentric Spatial Memory Tasks, although only the Egocentric test was able to discriminate between younger, middle, and older elderly participants. Learning effect was found in Allocentric Spatial Memory Task in younger and older groups, but not in the middle group. Allocentric and egocentric performance was not related to other visuospatial neuropsychological scores and gender did not influence performance in any task. Egocentric and Allocentric Spatial Memory Tasks may be useful tools in early screening for cognitive decline, as they are able to detect age differences in the cognitive unimpaired elderly population.

Microglia and neurons in the hippocampus of migratory sandpipers

The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.

Genetic basis of triatomine behavior: lessons from available insect genomes

Triatomines have been important model organisms for behavioural research. Diverse reports about triatomine host search, pheromone communication in the sexual, shelter and alarm contexts, daily cycles of activity, refuge choice and behavioural plasticity have been published in the last two decades. In recent times, a variety of molecular genetics techniques has allowed researchers to investigate elaborate and complex questions about the genetic bases of the physiology of insects. This, together with the current characterisation of the genome sequence of Rhodnius prolixus allows the resurgence of this excellent insect physiology model in the omics era. In the present revision, we suggest that studying the molecular basis of behaviour and sensory ecology in triatomines will promote a deeper understanding of fundamental aspects of insect and, particularly, vector biology. This will allow uncovering unknown features of essential insect physiology questions for a hemimetabolous model organism, promoting more robust comparative studies of insect sensory function and cognition.

Isla del Coco, on Cocos Plate, converges with Isla de San Andrés, on the Caribbean Plate, at 78mm/yr / La Isla del Coco, en la Placa de Cocos, converge con la Isla de San Andrés, en la Placa del Caribe, a 78 mm/año

Isla del Coco is the only land mass of the Cocos Plate that emerges above sea level. This makes it the only place where Cocos Plate motion can be measured using Global Navigation Satellite System (GNSS) monitoring. Global Positioning System (GPS) observations have been carried out sporadically over more than two decades on Isla del Coco, allowing precise measurement of the motion of the Cocos Plate. Recently, in May 2011, a continuous GPS station was built and instrumented at Isla del Coco, in Wafer Bay, by OVSICORI-UNA and UNAVCO, as part of the COCONet regional GNSS network. Position time series from this CGPS station (ISCO: Isla del Coco) show a steady motion of Isla del Coco at a speed of 90.9±1.5mm/yr in the N35oE direction in ITRF2008 and convergence with the Caribbean Plate at 78±1mm/yr. This result is consistent with the findings of the earliest GPS studies, and agrees within uncertainty with the estimated convergence rate of 76.4±x mm/ yr of the MORVEL plate motion model. MORVEL is based on an average over the last 780,000 years, and our result suggests that Cocos-Caribbean plate motions have been constant over that time interval.

La Isla del Coco es la única porción emergida en la placa del Coco. Esta condición la hace el único lugar donde se puede medir, usando Sistemas de Navegación Global por Satélite (GNSS), la velocidad de dicha placa. Las mediciones con GPS en la Isla del Coco se han realizado por más de dos décadas, permitiendo obtener velocidades precisas. En mayo del 2001 se instaló una estación continua de GPS en la Isla del Coco como parte, tanto de la Red Regional de GNSS COCONet, como del Sistema de Monitoreo Geodinámico de Nicoya (SISMOGENICO). Resultados de esta estación continua muestran movimiento continuo de la Isla del Coco, con respecto a ITRF2008, a una velocidad de 90.9±1.5mm/año con dirección N35oE y convergencia con la placa del Caribe a 78±1mm/año. Estas velocidades son consistentes con las obtenidas por MORVEL, un modelo geológico de velocidades de placas representativo de los últimos 780,000 años, y sugieren que la convergencia de estas placas se ha mantenido constante durante ese lapso de tiempo.